Automated devices, such as robots, include a manipulator, such as an arm, a spindle, or any other movable structure, whose movement is controlled by a computer. To increase the functionality of the automated device, the manipulator is typically fitted with an adapter for accepting different tools. Each of the different tools allows the manipulator to perform a different function. The adapter may accept, for example, machining tools, grasping tools, welding tools, etc. These different tools are typically stored in a tool magazine, and the automated device may be programmed to retrieve the different tools from the tool magazine as the tools are needed to perform various procedures.
One type of tool, known as a pickup tool or a pick-and-place tool, allows the manipulator to pick up a part, move the part to a desired location, and release the part at the desired location. One application of a pickup tool is in automated machining, such as, for example, computer automated machining (CAM), computer numerical control (CNC) machining, or robotic machining. In automated machining, for example, a pickup tool may be used to reconfigure a modular fixture. Configuration of a modular fixture is known as agile fixturing.
In automated machining, and more particularly agile fixturing, a fixture is a mechanical structure that supports a part being machined. A modular fixture is a fixture that can be reconfigured for use with different parts. A modular fixture may include a base to which various fixture elements, such as fixture locators, are removably attached. The base may be magnetic and the fixture elements, which act as supports for the part being machined, may be magnetically engaged with the base. Using a pickup tool, the manipulator may position the various fixture elements on the fixture base to correspond to the contours or other locating features of the part to be machined. The accuracy with which the manipulator locates the various fixture elements affects the accuracy with which the part is positioned relative to the automated machining device, and therefore the accuracy of the machining. Accordingly, for this and other applications, the pickup tool accepted by the manipulator must allow the pickup process to be performed accurately.
Furthermore, in agile fixturing, it is necessary for the pickup and reconfiguration operation to be reliable. Conventional pickup tools have a tendency to perform unreliably. For example, some conventional pickup tools do not have enough gripping force to overcome the magnetic force of the fixture base acting on a fixture element. This results in the fixture element slipping out of the pickup tool during a pickup operation, which is undesirable. Other pickup tools have a tendency to bind a fixture element inside the pickup tool, thereby resulting in the tool not being able to release the fixture element after picking it up.